A Field Programmable Gate Array (FPGA) capable of reconfiguring any logic function is widely used. A large number of reconfigurable logic circuits are provided in the FPGA, and a test is performed before shipping to check whether each logic circuit operates normally. In general, if some logic circuits are determined to have an error, the FPGA is discarded as a defective product. Also, if an error exists in the FPGA that has been mounted on a board, either the FPGA or the whole board needs to be replaced, and the defective board is discarded in the latter case. Such a replacement costs a manufacturer of the board using the FPGA product in terms of time and money.